This invention relates to the fabrication of interconnect layers using tungsten hard masks.
U.S. Pat. No. 6,087,269, issued Jul. 11, 2000, for a METHOD OF MAKING AN INTERCONNECT USING A TUNGSTEN HARD MASK discloses the fabrication of an interconnect layer using a tungsten hard mask by forming a tungsten-based layer over an aluminum-based layer. A polymer layer is deposited over the tungsten-based layer and patterned. The tungsten-based layer is patterned by applying a fluorine-based etchant using the polymer layer as an etch mask. Then the aluminum-based layer is patterned by applying a chlorine-based etchant using the tungsten-based layer as an etch mask.
Tungsten, however, doesn""t give off volatile compounds under the condition of a chlorine-based aluminum etch process. This means that tungsten-containing particles, pure tungsten as well as tungsten chlorides, are partially sputtering onto the wafer. This leads to shorts between different aluminum features and eventually to low electrical yields. The above-mentioned US patent gives no measures how to solve or avoid this problem.
Disclosed is a method of tungsten-based hard mask etching of a wafer, comprising providing a patterned tungsten-based hard mask atop a metal-based surface of said wafer, etching through said pattern with a plasma etch that is selective for said metal-based surface with respect to tungsten, and executing a flash etch selective for tungsten, said etch of at least a minimum duration effective in removing substantially all defects caused by tungsten particulate contaminating said wafer.
In another aspect of the first embodiment, said tungsten-based hard mask comprises a material selected from tungsten or an alloy thereof.
In another aspect of the first embodiment, said metal based surface comprises a material selected from aluminum or an alloy thereof.
In another aspect of the first embodiment, said plasma etch is a chlorine-based plasma etch.
In another aspect of the first embodiment, said chlorine-based plasma etch is executed using a plasma comprising a gas selected from boron trichloride, chorine, or mixtures thereof.
In another aspect of the first embodiment, said flash etch is a fluorine-based etch.
In another aspect of the first embodiment, said fluorine-based etch is a sulfur hexafluoride plasma etch.
In another aspect of the first embodiment, said fluorine-based etch is executed for a duration of from about 3 to about 5 seconds.
In another aspect of the first embodiment, said flash etch is executed for no more than 10 seconds.
In another aspect of the first embodiment, said flash etch is executed for a duration of from about 3 to about 5 seconds.
Disclosed is a second embodiment of a method of tungsten-based hard m ask etching of a wafer, comprising providing a patterned tungsten-based hard mask atop a metal-based surface of said wafer, etching through said pattern with a plasma etch comprising an effective amount of a first etchant that is selective for said metal-based surface with respect to tungsten and a lesser amount of a tungsten etchant, and executing a flash etch selective for tungsten, said etch of at least a minimum duration effective in removing substantially all defects caused by tungsten particulate contaminating said wafer.
In another aspect of the second embodiment, said tungsten-based hard mask comprises a material selected from tungsten or an alloy thereof.
In another aspect of the second embodiment, said metal based surface comprises a material selected from aluminum or an alloy thereof.
In another aspect of the second embodiment, said first etchant comprises a gas selected from boron trichloride, chorine, or mixtures thereof.
In another aspect of the second embodiment, said tungsten etchant is a fluorine-based etchant.
In another aspect of the second embodiment, said plasma etch is a chlorine-based etch comprising a lesser amount of fluorine-based etchant.
In another aspect of the second embodiment, said flash etch is a fluorine-based etch.
In another aspect of the second embodiment, said fluorine-based etch is a sulfur hexafluoride plasma etch.
In another aspect of the second embodiment, said fluorine-based etch is executed for a duration of from about 3 to about 5 seconds.
In another aspect of the second embodiment, said flash etch is executed for no more than 10 seconds.